Multi-channel cochlear implants (CIs) are designed to provide frequency-specific information to the recipient by stimulating different sites within the cochlea. However, the presence of multiple stimulation sites within the cochlea increases the risk of interaction between these sites. Channel interaction is a phenomenon that can occur when electrodes in a CI stimulate overlapping neural populations. When multiple electrodes are stimulated simultaneously, current fields from each electrode can sum or subtract prior to neural stimulation. The perceptual result can be a stimulus that is either uncomfortably loud or inaudible. When 2 electrodes are stimulated in rapid succession, nerve fibers become refractory in response to the first electrode and are thus unable to respond to the second electrode. As a result, some information in the speech signal may not be adequately encoded by the auditory periphery, which might have negative effects on speech perception performance with the CI. Previous research has shown that channel interaction can be measured both psychophysically and physiologically, but little is known about the extent to which these 2 measures are related. Psychophysical measures of channel interaction may be useful for making decisions about creating optimal speech processor programs for individual CI recipients. Unfortunately, making detailed psychophysical measures is not clinically feasible because it is time consuming and generally not possible with pediatric CI recipients. However, peripheral measures of channel interaction can be made relatively quickly with physiologic techniques. The overall goal of this application is to determine how physiologic measures of channel interaction are related to psychophysical measures of channel interaction, and if either of these measures can aid the clinician in choosing optimal speech processing parameters for individual CI recipients. The proposed experiments are designed to: (1) investigate the relation between physiologic and psychophysical measures of channel interaction for non-simultaneous stimulation; (2) investigate the relation between physiologic and psychophysical measures of channel interaction for simultaneous stimulation; and (3) investigate the relation between channel interaction and speech perception performance using speech processing strategies that employ both simultaneous and non-simultaneous stimulation modes. [unreadable] [unreadable]